Kids Research Express

Watt, James (1736-1819), Scottish inventor and mechanical engineer, renowned for his improvements of the steam engine. Watt was born on January 19, 1736, in Greenock, Scotland. He worked as a mathematical-instrument maker from the age of 19 and soon became interested in improving the steam engines, invented by the English engineers Thomas Savery and Thomas Newcomen, which were used at the time to pump water from mines. Watt determined the properties of steam, especially the relation of its density to its temperature and pressure , and designed a separate condensing chamber for the steam engine that prevented enormous losses of steam in the cylinder and enhanced the vacuum conditions. Watt's first patent, in 1769, covered this device and other improvements on Newcomen's engine, such as steam-jacketing, oil lubrication, and insulation of the cylinder in order to maintain the high temperatures necessary for maximum efficiency. At this time, Watt was the partner of the British in...

Scheele, Carl Wilhelm (1742-1786), Swedish chemist, noted for his discovery of a great number of elements, compounds, and chemical reactions. Scheele was born in Stralsund, Germany, which at that time was the capital of Swedish Pomerania. He had no formal training in chemistry and studied the elements of science while apprenticed to an apothecary. In 1770 he came under the guidance of Swedish chemist Torbern Bergman. In 1775 Scheele became the proprietor of a pharmacy in Köping, Sweden, where he continued his chemical research. He is credited with the identification of the elements chlorine and barium, but Scheele believed that they were compounds, not elements. British chemist Sir Humphrey Davy recognized chlorine and barium as elements in the early 1800s. Scheele prepared oxygen from various oxides independently of and somewhat before English chemist Joseph Priestley , who is credited with the discovery of the element. He was the first to prepare many compounds, including tartaric a...

Priestley, Joseph (1733-1804), British chemist, who isolated and described several gases, including oxygen , and who is considered one of the founders of modern chemistry because of his contributions to experimentation. Priestley was born on March 13, 1733, in Fieldhead, Yorkshire, the son of a Calvinist minister. Priestley trained as a minister of the Dissenting church, which comprised various churches that had separated from the Church of England. He was educated at Daventry Academy, where he became interested in physical science. His first ministry was at Needham Market, Suffolk, in 1755, and he was minister at Nantwich from 1758 to 1761. Later he became a tutor at Warrington Academy in Lancashire, where he was noted for his development of practical courses for students planning to enter industry and commerce. He also wrote a text, Rudiments of English Grammar (1761), which differed from older, classical approaches. He was ordained in 1762. Priestley was encouraged to conduct experi...

Franklin, Benjamin (1706-1790), American printer, author, diplomat, philosopher, and scientist, whose many contributions to the cause of the American Revolution (1775-1783), and the newly formed federal government that followed, rank him among the country’s greatest statesmen. Franklin was born on January 17, 1706, in Boston. His father, Josiah Franklin, a tallow chandler by trade, had 17 children; Benjamin was the 15th child and the 10th son. His mother, Abiah Folger, was his father’s second wife. The Franklin family was in modest circumstances, like most New Englanders of the time. After his attendance at grammar school from age eight to ten, Benjamin was taken into his father’s business. Finding the work uncongenial, however, he entered the employ of a cutler. At age 13 he was apprenticed to his brother James, who had recently returned from England with a new printing press. Benjamin learned the printing trade, devoting his spare time to the advancement of his education. His reading...

CGS System, also centimeter-gram-second system (usually written “cgs system”), a metric system based on the centimeter (c) for length, the gram (g) for mass , and the second (s) for time. It is derived from the meter-kilogram-second (or mks) system but uses certain special designations such as the dyne (for force ) and the erg (for energy ). It has generally been employed where small quantities are encountered, as in physics and chemistry .

Clocks and Watches, devices used to measure or indicate the passage of time . A clock, which is larger than a watch, is usually intended to be kept in one place; a watch is designed to be carried or worn. Both types of timepieces require a source of power and a means of transmitting and controlling it, as well as indicators to register the lapse of time units. In a clock, the source of power may be produced by weight, a mainspring, or an electric current. Except in electric or electronic clocks, periodic adjustments, such as lifting the weight or tightening the spring, are needed. The motive force generated by the power source in a mechanical clock is transmitted by a gear train and regulated by a pendulum or a balance wheel. In such a clock, the time may be reported audibly by the striking of a gong or chime and is registered visually by the rotation of wheels bearing numerals or by the position of hands on a dial. In electric or electronic clocks, time may be shown by a display of nu...

Dentistry, practice of preventing and treating diseases of the teeth , gums, and tissues of the mouth. Unlike other human tissue, such as skin, that continuously grows and self-rejuvenates, dental structures generally cannot repair themselves and require regular care to retain their health and vitality. If not treated, dental health problems can lead to complications in other parts of the body. Thorough and timely dental care is not only important for maintaining healthy teeth and gums, it is essential to overall human health. Dentists and dental hygienists are health care professionals trained and licensed to provide dental care. General dentistry emphasizes treatments that prevent oral health problems, especially dental caries, commonly called tooth decay. Tooth decay is one of the most prevalent diseases in the United States, second only to the common cold. Dentists help prevent tooth decay by cleaning teeth to remove buildup of calculus, or tartar, which forms when plaque, a sticky...